CVE-2021-43840 – Path traversal in message_bus

https://notcve.org/view.php?id=CVE-2021-43840

message_bus is a messaging bus for Ruby processes and web clients. In versions prior to 3.3.7 users who deployed message bus with diagnostics features enabled (default off) are vulnerable to a path traversal bug, which could lead to disclosure of secret information on a machine if an unintended user were to gain access to the diagnostic route. The impact is also greater if there is no proxy for your web application as the number of steps up the directories is not bounded. For deployments which uses a proxy, the impact varies. For example, If a request goes through a proxy like Nginx with `merge_slashes` enabled, the number of steps up the directories that can be read is limited to 3 levels. • https://github.com/discourse/message_bus/commit/9b6deee01ed474c7e9b5ff65a06bb0447b4db2ba https://github.com/discourse/message_bus/security/advisories/GHSA-xmgj-5fh3-xjmm • CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') •